Sleep sack



FIG. 1 is a front view of the sleep sack of the present invention;

FIG. 2 is a left side view thereof;

FIG. 3 is a back side view thereof;

FIG. 4 is a right side view thereof; and,

FIG. 5 is a front perspective view of the sleep sack, showing it unzipped and fully opened.

The broken lines in the drawings are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a sleep sack, as shown and described. 